Question

What is the concentration of a solution of iron(II) sulfate if its absorbance at a wavelength of 495 nm is 0.456 in a 1 cm cuvette with a path length of 1 cm? The molar absorptivity of iron(II) sulfate at 495 nm is 8100 L/mol·cm. The molecular weight of iron(II) sulfate is 151.91 g/mol.

Answer 1

To find the concentration of the solution, we can use the Beer-Lambert Law, which states:A =  * c * lwhere A is the absorbance,  is the molar absorptivity, c is the concentration, and l is the path length.We are given the following values:A = 0.456 = 8100 L/molcml = 1 cmWe need to solve for c  the concentration :c = A /   * l c = 0.456 /  8100 L/molcm * 1 cm c = 0.456 / 8100 L/molc  5.63 x 10^-5 mol/LNow we have the concentration in mol/L, but we need to convert it to g/L using the molecular weight of iron II  sulfate:mass = concentration * molecular weightmass = 5.63 x 10^-5 mol/L * 151.91 g/molmass  0.00855 g/LSo, the concentration of the iron II  sulfate solution is approximately 0.00855 g/L.